array_key_exists
(PHP 4 >= 4.1.0, PHP 5)
array_key_exists -- Checks if the given key or index exists in the array
Description
bool
array_key_exists ( mixed key, array search)
array_key_exists() returns TRUE if the
given key is set in the array.
key can be any value possible
for an array index. array_key_exists() also works
on objects.
Example 1. array_key_exists() example
<?php
$search_array = array('first' => 1, 'second' => 4);
if (array_key_exists('first', $search_array)) {
echo "The 'first' element is in the array";
}
?>
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Note:
The name of this function is key_exists()
in PHP 4.0.6.
Example 2. array_key_exists() vs isset()
isset() does not return TRUE for array keys
that correspond to a NULL value, while
array_key_exists() does.
<?php
$search_array = array('first' => null, 'second' => 4);
// returns false
isset($search_array['first']);
// returns true
array_key_exists('first', $search_array);
?>
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See also isset(),
array_keys(), and
in_array().